the extra 4 channels are usually used for effects/another deck to sample off, your choice if you want to haev them now or worry about it later, this little guy isnt really the most feature rich mixer... for that price, try to break it down like this... a used CDJ1000mk3 goes for about lets say $800 max so $1600 for 2, that means your paying $400 - $700 for a DJM400 mixer? they are only $800 brand new... Ebay brand new DJM400 i think your paying a little too much, for $2000 its an ok deal but i wouldnt go above that